If you spend a lot of time online, it would certainly seem that way.
Or spend a lot of time with certain demographics. My parents don't know what ao3 is, but a couple of female coworkers are huge fans
Edit: according to [1] 93% of users are 44 or younger, and women outnumber men 10:1
[1] https://www.flowjournal.org/2023/02/fan-demographics-on-ao3/
alt Hacker News
Or spend a lot of time with certain demographics. My parents don't know what ao3 is, but a couple of female coworkers are huge fans
Edit: according to [1] 93% of users are 44 or younger, and women outnumber men 10:1
[1] https://www.flowjournal.org/2023/02/fan-demographics-on-ao3/